Thermal management system for embedded environment and method for making same

ABSTRACT

A thermal management system for an embedded environment is described. The thermal management system includes a pleumo-jet that has at least one wall defining a chamber, at least one piezoelectric device on the at least one wall, and a compliant material within the at least one wall and encompassing the chamber. The compliant material has at least one opening providing fluid communication between said chamber and the embedded environment. A cooling system is also described. A method for making a pleumo-jet is also described.

BACKGROUND

The invention relates generally to thermal management systems, and moreparticularly to thermal management systems for use in embeddedenvironments.

Environments having embedded electronic systems, hereinafter embeddedenvironments or heated environments, offer challenges for thermalmanagement. Such systems produce waste heat as a part of their normaloperation, heat that must be removed for proper performance andreliability of the embedded electronics. The design of thermalmanagement systems to provide cooling for embedded electronics is aformidable challenge due to space limitations. Examples of embeddedelectronic systems include single board computers, programmable logiccontrollers (PLCs), operator interface computers, laptop computers, cellphones, personal digital assistants (PDAs), personal pocket computers,and other small electronic devices, there is a limited amount ofavailable space for thermal management systems. It has been known to usepassive cooled heat sinks or forced air-cooling as thermal managementsystems to assist in the removal of heat from electronic components.Further, it has been known that conducting the heat generated byelectronic components to a printed circuit board, on which they aremounted, thereby providing a migration of the heat from a smaller areato a larger area.

SUMMARY

The invention includes embodiments that relate to a thermal managementsystem for a heated environment that includes a pleumo-jet. Thepleumo-jet includes at least one wall defining a chamber, at least oneactive material on the at least one wall, and a compliant materialwithin the at least one wall and encompassing the chamber. The compliantmaterial has at least one opening facilitating fluid communicationbetween the chamber and the heated environment.

The invention includes embodiments that relate to a pleumo-jet thatincludes a first flexible structure, a second flexible structure, atleast one active material on at least one of the first and secondflexible structures, and a compliant material positioned between thefirst and second flexible structures and defining a chamber. Thecompliant material includes at least one orifice for facilitating fluidcommunication between the chamber and an ambient environment.

The invention includes embodiments that relate to a cooling system for aheated environment. The cooling system includes a substrate having onefree end and one anchored end, at least one piezoelectric devicepositioned on the substrate, and an electrical circuit to provide anelectrical current to the at least one piezoelectric device.

The invention includes embodiments that relate to a method for making apleumo-jet. The method includes providing a pair of flexible structures,at least one of the structures having an attached active material,attaching a compliant material between the pair of flexible structures,the elastomeric material having at least one orifice, and addingelectrical contacts to the pair of flexible structures.

These and other advantages and features will be more readily understoodfrom the following detailed description of preferred embodiments of theinvention that is provided in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of a thermal management systemutilizing a pleumo-jet constructed in accordance with an embodiment ofthe invention.

FIG. 2 is a cross-sectional side view showing the thermal managementsystem of FIG. 1 with the pleumo-jet in a different position.

FIG. 3 is a top view of a thermal management system constructed inaccordance with an embodiment of the invention.

FIG. 4 is a cross-sectional side view of the thermal management systemof FIG. 3 taken along line IV-IV.

FIG. 5 is a top view of a pleumo-jet constructed in accordance with anembodiment of the invention.

FIG. 6 is a top view of a pleumo-jet constructed in accordance with anembodiment of the invention.

FIG.7 is a side view of the pleumo-jet of FIG. 6.

FIG. 8 is a schematic view a thermal management system utilizing apiezoelectrically driven flexible cooling apparatus constructed inaccordance with an embodiment of the invention.

FIG. 9 is a schematic view showing the thermal management system of FIG.8 with the piezoelectrically driven flexible cooling apparatus in adifferent position.

FIG. 10 illustrates process steps for forming a pleumo-jet in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, there is shown a thermal management system10 that includes a pleumo-jet 12 illustrated in cross-section and placedin proximity to a printed circuit board assembly (PCA) 30 having aplurality of electronic components to be cooled 32 _(a-d). While a PCA30 is depicted with reference to an embodiment of the invention, itshould be appreciated that the thermal management system 10 may beutilized in any suitable embedded environment and its depiction withreference to the PCA 30 is merely for convenience in description. ThePCA 30 may be used in heated environments in any number of smallelectronic devices, such as, for example, single board computers,programmable logic controllers (PLCs), laptop computers, cell phones,personal digital assistants (PDAs), personal pocket computers, to name afew. The pleumo-jet 12 is sized appropriately for its use, and generallyis in the meso-scale or micro-scale.

The pleumo-jet 12 is positioned such that a pulsating fluid stream ofambient air can be generated from the apparatus 12 and directed at theelectronic components to be cooled 32 _(a-d). As shown, in FIG. 1, afluid stream of ambient air, or other fluid, is directed along directionA toward the electronic component to be cooled 32 _(b). Alternatively,the pleumo-jet 12 may be positioned to direct a fluid stream of ambientair along direction B toward the electronic component to be cooled 32_(b) (FIG. 2).

The pleumo-jet 12 includes a first structure or wall 14 and a secondstructure or wall 16. The walls 14, 16 are formed of a flexiblematerial, such as, for example, metal, foil, plastic, or polymercomposite material. A compliant material 18 is positioned between thepair of walls 14, 16, and the combination of the walls 14, 16 and thecompliant material 18 define a chamber 20. At least one orifice 22provides a channel between the chamber 20 and the environment outsidethe apparatus 12. Although a pair of opposing walls 14, 16 are depicted,it should be appreciated that instead of two walls, a single wall(wrapping around to form a cylinder) along with the compliant material18 may form a pleumo-jet, such as the pleumo-jet 12.

Positioned on at least one of the walls 14, 16 is an active material,such as, for example, a piezoelectric material. As shown, activematerials 24 and 26 are positioned, respectively, on walls 14 and 16. Asuitable active material is one which is capable of creating stressresulting from an electrical stimulus. Examples of suitable activematerial include piezoelectric material, magnetostrictive material(magnetic fields from coils attract/oppose one another), shape-memoryalloy, and motor imbalance (motor with a mass imbalance createsoscillatory motion). Within the subset of piezoelectric materials,suitable active materials include bimorph piezoelectric configurations,where two piezo layers are energized out of phase to produce bending;thunder configurations, where one piezo layer is disposed on apre-stressed stainless steel shim; buzzer element configurations, whereone piezo layer is disposed on a brass shim; and MFC configurations,where a piezo fiber composite on a flexible circuit is bonded to a shim.

The active material 24, 26 may incorporate a ceramic material.Electrical circuitry (schematically depicted in FIG. 8) is attached tothe pleumo-jet 12 to provide an electrical current to one or both of theactive material 24, 26. The current may be provided as a sine wave, asquare wave, a triangular wave, or any other suitable waveform, and itshould be appreciated that the current is not to be limited to anyspecific wave form. Specifically, it has been found that currents havinglower harmonics, such as, for example, a sine wave may be used toprovide a quieter pleumo-jet 12.

FIGS. 3 and 4 illustrate a thermal management system 110 in accordancewith another embodiment of the invention. The thermal management system110 includes a pleumo-jet system 111, which has a plurality ofpleumo-jets in a stacked arrangement. As shown, the pleumo-jet system111 includes pleumo-jets 112 _(a), 112 _(b), and 112 _(c) in a stackedarrangement. The pleumo-jet 112 _(c) is positioned over a base 129 andsupported in that location with one or more supports 127. Thepleumo-jets 112 _(a), 112 _(b), and 112 _(c) have a similar constructionto the pleumo-jet 12 (FIGS. 1, 2), with the optional exception of theorifices. Specifically, each of the pleumo-jets 112 _(a), 112 _(b), and112 _(c) includes flexible walls and a compliant material defining achamber 120, and each of the flexible walls has one or more activematerials (not shown). Supports between the pleumo-jets 112 _(a), 112_(b), and 112 _(c) are necessary to provide sufficient room toaccommodate the active materials on one or both flexible walls of eachpleumo-jet.

Each pleumo-jet 112 _(a), 112 _(b), and 112 _(c) may include a singleorifice 122 extending from the chambers 120 through the compliantmaterial. The pleumo-jet system 111 may be arranged such that each ofthe single orifices 122 of each pleumo-jet 112 _(a), 112 _(b), and 112_(c) is positioned in the same direction (FIG. 4). Alternatively, eachof the single orifices 122 may be positioned to direct ambient air in adifferent direction than the other single orifices 122 (FIG. 3). For anytwo adjacent orifices 122, the separation between the orifices 122 maybe in a range between just above zero degrees (0°) to less than ninetydegrees (90°). In one embodiment, adjacent orifices 122 may be separatedby a range of about 5° to about 45°.

The pleumo-jets 112 _(a), 112 _(b), and 112 _(c) are surrounded by fins128, which are supported on the base 129. The fins 128 assist inincreasing the surface area for heat transfer for cooling the electroniccomponents 32 _(a-d). As with the previously described pleumo-jet 12,the pleumo-jets 112 _(a), 112 _(b), and 112 _(c) utilize activematerial, for example a piezoelectric material (not shown), to formstreams of ambient air. Briefly, electrical current from electricalcircuitry (shown in FIG. 8) is received by the active material, andtransformed into mechanical energy. The electrical current can take theform of a sine wave, a square wave, a triangular wave, or any othersuitable wave form. The voltage level for the electrical current may bebetween 1 and 150 volts but is not so limited. The frequency of thecurrent may be between 2 and 300 hertz for embodiments requiring reducednoise, and between 300 hertz and 15 kilohertz for embodiments that donot require reduced noise levels.

The active material creates stress on the flexible walls, causing themto flex inwardly, resulting in a chamber volume change and an influx ofambient air into the chambers 120, and then outwardly, thereby ejectingthe ambient air from the chambers 120 via the orifices 122.

Another alternative embodiment of a pleumo-jet system is illustrated inFIG. 5. Specifically, a pleumo-jet system 211 is illustrated asincluding a base 229 supporting a pleumo-jet 212. The pleumo-jet 212 hasa plurality of orifices 222, each extending outwardly in differentradial directions. An active material 224 is shown on a surface of aflexible wall of the pleumo-jet 212. For any two adjacent orifices 222,the separation between the orifices 222 may be in a range between justabove 0° to less than 90°. In one embodiment, adjacent orifices 222 maybe separated by a range of about 5° to about 45°.

FIGS. 6 and 7 illustrate a pleumo-jet 312. The pleumo-jet 312 includes afirst flexible wall or structure 314, a second flexible wall orstructure 316, and a compliant material 318 positioned between theflexible walls 314, 316. The walls 314 and 316 are rectangular in shapeand, together with the compliant material 318, form a chamber (notshown). Orifices 322 extend out through the compliant material 318 fromthe chamber to the ambient environment. An active material 324 ispositioned on the wall 314, and optionally an active material 326 may bepositioned on the wall 316. The active material can be activated with anelectric current provided by electrical circuitry (not shown) to createstress on the wall(s) 314 (and 316) to allow for the ingestion ofambient air into the chamber and the expulsion of the ambient air fromthe chamber to the ambient, heated environment.

FIGS. 8 and 9 illustrate another embodiment of a thermal managementsystem. A thermal management system 410 is illustrated as including apiezoelectric fan apparatus 412 in working relationship with a PCA 30containing electronic components to be cooled 32 _(a-d). The piezo fanapparatus 412 includes one free end and one end fixed to a supportmember 420. The piezo fan apparatus includes a substrate 414 and anactive material 416. The active material 416 may utilize, for example, apiezoceramic material.

An electrical circuit 418 is connected to the piezo fan apparatus 412.Running an electrical current through the piezo fan apparatus 412 sendsan electrical charge through the active material 416. The activematerial 416 transforms the electrical energy into mechanical energy bycreating a stress on the substrate 414, causing it to rotate about thefixed end. This creates a current of ambient air to travel in adirection C (FIG. 8) or in a direction D (FIG. 9), depending upon thepositioning of the piezo fan apparatus 412 relative to the electroniccomponents to be cooled 32 _(a-d).

Next, and with specific reference to FIG. 10, will be discussed aprocess for forming a pleumo-jet in accordance with an embodiment of theinvention. At Step 500, a pair of flexible structures is provided. Theflexible structures may be metallic or they may be non-metallic, such asplastic or polymer composite material. Examples of the flexiblestructures include flexible walls 14, 16 (FIGS. 1, 2) and flexible walls314, 316 (FIGS. 6, 7). One or both of the flexible structures require anactive material that is excitable by an electrical stimulus to beaffixed thereon. Suitable examples of active material include material24, 26 (FIGS. 1, 2) and material 324, 326 (FIGS. 6, 7).

At Step 505, a compliant material is attached between the flexiblestructures. The compliant material may be compliant material 18 (FIGS.1, 2) or compliant material 318 (FIGS. 6, 7). The compliant material isto be provided in such a form as to define a chamber between theflexible structures. One process for providing the compliant material isto dispense the compliant material in a liquid or semi-liquid form ontoone of the flexible structures, placing the other conductive structureon the compliant material, and allowing the compliant material to dry. Aliquid silicone-based material may be suitable for such a process.Another process for providing the compliant material is to cut thecompliant material from a pre-made sheet of compliant material, andbonding the pre-made sheet of cut compliant material to the flexiblestructures. A pre-made silicone-based sheet of material may be suitablefor this process.

At Step 510, electrical contacts are provided to the flexiblestructures. Electrical circuitry will be attached to the electricalcontacts.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. A thermal management system for a heated environment, comprising: apleumo-jet, comprising: at least one wall defining a chamber; at leastone active material on said at least one wall; and a compliant materialwithin said at least one wall and encompassing said chamber, saidcompliant material having at least one opening facilitating fluidcommunication between said chamber and the heated environment.
 2. Thethermal management system of claim 1, wherein said compliant materialcomprises an elastomeric material.
 3. The thermal management system ofclaim 1, comprising an electrical circuit to provide an electricalcurrent to said pleumo-jet.
 4. The thermal management system of claim 3,wherein said electrical current is one exhibiting lowered harmonics. 5.The thermal management system of claim 4, wherein said electricalcurrent omprises a sine wave.
 6. The thermal management system of claim1, wherein the heated environment includes single board computers,programmable logic controllers (PLCs), operator interface computers,laptop computers, cell phones, personal digital assistants (PDAs), andpersonal pocket computers.
 7. The thermal management system of claim 1,wherein the heated environment comprises at least one heated body. 8.The thermal management system of claim 7, wherein said at least oneopening is positioned to eject an ambient fluid directly on said atleast one heated body.
 9. The thermal management system of claim 8,wherein said at least one opening is at an angle transverse to an uppersurface of the at least one heated body.
 10. The thermal managementsystem of claim 1, wherein said elastomeric material comprises aplurality of openings facilitating fluid communication between saidchamber and the heated environment.
 11. The thermal management system ofclaim 10, wherein said at least one wall has a circular profile.
 12. Thethermal management system of claim 10, wherein said at least one wallhas a rectangular profile.
 13. The thermal management system of claim 1,comprising: a base upon which said pleumo-jet is positioned; and aplurality of fins surrounding said pleumo-jet.
 14. The thermalmanagement system of claim 13, comprising a plurality of pleumo-jetspositioned on said base in a stacked arrangement.
 15. The thermalmanagement system of claim 1, wherein said pleumo-jet comprises a pairof walls sandwiching said elastomeric material, each of said wallshaving said at least one piezoelectric device.
 16. A pleumo-jet,comprising: a first flexible structure; a second flexible structure; atleast one active material on at least one of said first and secondflexible structures; and a compliant material positioned between saidfirst and second flexible structures and defining a chamber, whereinsaid compliant material comprises at least one orifice for facilitatingfluid communication between said chamber and an ambient environment. 17.The pleumo-jet of claim 16, comprising an electrical circuit to providean electrical current to the at least one active material.
 18. Thepleumo-jet of claim 16, wherein said compliant material comprises anelastomeric material.
 19. The pleumo-jet of claim 16, wherein saidapparatus is no larger than meso-scale sized.
 20. The pleumo-jet ofclaim 16, wherein said at least one active material comprises apiezoceramic material.
 21. The pleumo-jet of claim 16, wherein said atleast one active material is positioned on both of said first and secondflexible structures.
 22. A cooling system for a heated environment,comprising: a substrate having one free end and one anchored end; atleast one piezoelectric device positioned on said substrate; and anelectrical circuit to provide an electrical current to the at least onepiezoelectric device.
 23. The cooling system of claim 22, wherein theheated environment includes single board computers, programmable logiccontrollers (PLCs), operator interface computers, laptop computers, cellphones, personal digital assistants (PDAs), and personal pocketcomputers.
 24. The cooling system of claim 22, wherein said substrate isno larger than meso-scale sized.
 25. A method for making a pleumo-jet,comprising: providing a pair of flexible flexible structures, at leastone of the structures having an attached active material; attaching acompliant material between the pair of flexible structures, saidelastomeric material having at least one orifice; and adding electricalcontacts to the pair of flexible structures.
 26. The method of claim 25,wherein said providing comprises providing attached active material foreach of the pair of flexible flexible structures.
 27. The method ofclaim 25, wherein said attaching comprises attaching an elastomericmaterial between the pair of flexible structures.
 28. The method ofclaim 25, wherein said attaching comprises: dispensing the compliantmaterial as a semi-liquid silicone-based material; contacting thesemi-liquid silicon-based material with one of the flexible structures;and placing the other of the flexible structures in contact with thesemi-liquid silicone-based material.
 29. The method of claim 25, whereinsaid attaching comprises: forming the compliant material from a pre-madesheet of silicone-based material; and bonding the compliant material tothe pair of flexible structures.